Hydraulic tensioning devices for chain or belt drives are known in the prior art. A tensioning device according to the class is described in DE 198 28 309 A1. In that document, a piston is arranged so that it can move in the axial direction in an element functioning as a hydraulic cylinder, wherein hydraulic fluid is located in the resulting inner space. The problem-free functioning of the desired hydraulic damping effect requires the ventilation of the system. To this end, the housing of the known tensioner carrying the cylinder has a ventilation opening.
DE 20 2007 002 456 U1 exhibits a similar solution. Also here, in a piston-cylinder system, a ventilation device is arranged that is sealed here with a valve body in the form of a ball.
The production of the ventilation possibility requires relatively high production-related expenses in the known solutions. This results in corresponding costs, not only costs concerning the production of the required parts, but also with respect to the assembly of the tensioner.